Résumé
Metal and nitrogen-doped carbons electrocatalysts (M-N-C, where M is Fe or Co) are investigated for the oxygen reduction reaction (ORR) in alkaline conditions in the presence of borohydride ions (BH4-). The electrochemical properties of the Fe-N-C and Co-N-C catalysts were investigated by cyclic voltammetry and rotating disk electrode techniques: their ORR electrocatalytic activity was bridged to their physico-chemical properties, mainly type of metallic center (Fe vs. Co), structure (atomic dispersion vs. nanoparticles) and BET surface area. It is found that Fe-N-C catalysts have the best performances for the ORR electrocatalysis, even in presence of BH4- anions. The atomically-dispersed Fe- and Co-containing electrocatalysts reach better BH4--tolerance than their counterparts baring nanoparticles. For the atomically dispersed Fe-N-C electrocatalysts, the lowest BET surface area material generates a slight advantage of ORR mass activity and a poor (and desired) activity for borohydride oxidation reaction (BOR).